The ultimate objective of this work is to arrive at a fundamental understanding of the role played by the cell surface in growth regulation, using Neurospora as a model system. A more immediate objective is to pinpoint the role played, in growth regulation and in cellular adhesion, by a galactosamine-rich polymer (MP) which is a component of the Neurospora surface. The relevance of the ultimate objective to the conquest of cancer is obvious in the light of current knowledge concerning mammalian cells, normal and malignant. The more immediate objective may also be relevant to cancer as MP has been shown to interact differentially with normal and malignant cells. The plan for this third project year is not essentially different from the one outlined initially, which included kinetic studies on the interaction between Neurospora and added MP, and strain and culture comparisons of quantities and kinds of MP in order to better understand its physiological role. A new tool available this year is a purified enzyme preparation which partially degrades and inactivates MP.